Masking paper such as for lithography



Oct 21, 1947- F. A. MARTY` MASKING PAPER SUCH AS FOR LITHOGRAPHY Illu l Illlvllu v au ,MS y

INVENTOR ,7km/

ATTRNEYS Patented Oct. 21, 1947 UNITED STATES PATENT oFFIcEQ MASKING PAPER SUCH AS FOR LITHOGRAPH I Frank A. Marty, Flushing,vv N. Y. Application November 16, 1944, Serial No. 563,807

6 Claims. (Cl. 88-109) The invention relates to a paper designed particularly as a masking paperior lithographie stripping. In the layout ofl lithographie work, a negative is held in a desired position by a masking sheet and the desired extent of the negative 4to be printed on the lithographie plate is determined by cutting out or stripping the paper to the desired dimensions, shape and in its desired position. Such a lithographie masking sheet must be suficiently transparent to the light from an incandescent lamp so that the matter or negative to be lithographed will be'clearly visible therethrough for the layout and yet be impenetrable to the lithographie printing light such as a mercury vapor lamp. l v

It is an object of the invention to construct a lithographie masking paper particularly suitable `for lithographie wor Another object of the invention is to construct a masking sheet for lithographie work the kcolor of which is sealed in and will not rub oif.

Another object is to provide a masking sheet to which AScotch tape or other adhesive strip will adhere thereto and yet will readily pull off from the sheet.

Another object is to construct a masking sheet which will readily take pen ink, pencil or litho ink marks and lines.

A still further object is to construct a masking sheet which does not shrink or stretch under the usual conditions existing where lithographie workI is done.

Other objects of the invention will appear more fully from the following description and the accompanying drawing in which the figure illustrates an enlarged portion of a masking sheet.

The masking paper of the invention utilizes a base sheet I which is orange or yellow in color because these colors are impenetrable to light used for lithographie work such as the mercury vapor lamp. The dye of the base sheet should be insensible to alkali. This base sheet is preferably first coated with a mixture of silicate of soda with an equalizer material such as gelatin or latex in they proportions of about one part of water glass to nine partsof equalizer. This first coat 2 could be dispensed with although'it improves the characteristics of the sheet so far as stretching and shrinking is concerned and also improves the cutting properties to give a sharp clear cut edge. The proportions of silicate of soda and an equalizer will vary with the type of paper used for example the proportion referred to is that best suited for ground wood paper and increasing amounts forl the following in the order named,

Y tion of rags.

-or when su 2 A sulphite, sulphate, sulka, rags, and combina- The equalizer is used to give the sheet greater flexibility or to make the sheet less brittle. l

A coating 3 of clay ith a sizing such as casein or starch is next appliedto the sheet. Therclay is preferably a white clay whiclnsoftens the yellow or orange to a pastel shade, andghence is less glaring upon the eyes. A hardening agent, such as formaldehyde, maybe used-in the clay mixture to hardenA the clay coating so thatiitdoesnot chalk off of thesheet. The amount of formalde` hyde used will vary and for best results enough is used so that the sheet will withstand a s'eve point or pick wax test of the surface. An equalizer'may also be used with the clay coating to render the sheet less brittle.

A third coating 4 is applied tothe sheet over the clay coating which is made up of a mixture of silicate of soda with `an equalizer preferably in the proportions of about seven and one half parts of silicate of soda and two and a half parts of equalizer for best results. There may be considerable variation in theseproportions. g `'Ihe sheet which results is largely resistant to moisture and temperature and retains its dimensionswvith no or slight stretch or shrinkage irrespective of. changes'in humidity of the atmosphere ject to the heat fromV a lighted stripping table. The sheet is transparent to ordinary lightsothat a negative which is secured to the under side of the sheetmay be clearly seen therethrough. The pastel salmon color` brings' out the lines on the underlying negative with clear cut lines through and is restful to the` eyes. The surface of the sheet is of such character that Scotch tape and other adhesives will readily-.stick thereto tb hold a negative in place upon the sheet; and yet the surfacek permits easy removal of the Scotch tape and relatively freerem'oval of other adhesive strips. The surface also is of s uch character-that it can be written on with pencil, ordinary ink or litho ink.

The treatment seals in -the dye of the base sheet with the result that smearing of the dye of the stock sheet cannot occur. Furthermore thekerosene used with paper negatives does not affect the transparency of the paper norA smear the masking sheet do occur to those skilled in the art, especially after benefiting from the teachings of an invention. Hence, it will be understood that this disclosure is illustrative of preferred means of embodying the invention in useful form by explaining the construction, and advantages thereof.

What is claimed is: l

1. A lithographie masking paper comprising a stock sheet dyed an orange to a yellow color which is relatively transparent and the dye of which is insensitive to alkali, a coating of a mixture of clay and a sizing upon the sheet of stock, and a coating of a mixture of silicate of soda and an equalizer over the clay coating.

2. Alithographic masking paper comprising a stock sheet dyed an orange to a yellow color which j is relatively transparent and the dye of which is insensitive ltoalkali, a coating upon the stock sheet includinga mixture of silicate of soda and an equalizer, a coating of clay mixed with a sizing over the first coating, and a. secondcoating of a mixture of silicate of soda vand an equalizer over the clay-coating.

3. A lithographie masking paper comprising a stock sheet dyed an orange to a yellow color which is relatively transparent and the dye of which is insensitive to alkali, a coating upon the paper of a mixture'of silicateoi soda and an equalizer, a coating of clay mixed with sizing and a hardening agent, and a second coating of a mixture of silicate of soda with an equalizer.

4. A lithographie masking paper comprising a stock sheet dyed an orange to a yellow color which is relativelytransparent and the dye of which is insensitive to alkali, a coating upon the paper of a mixtureof about one part of silicate of soda and nine parts of an equalizer, a coating of clay mixed with sizing and a hardening agent, and a second coating of a mixture of about seven and a half parts of silicate of soda and two and a and a half parts of silicate of soda and two and a half parts of an equalizer over the clay coating.

6. A lithographie masking paper comprising a stock sheet dyed an orange to a yellow color which is relatively transparent and the` dye of which is insensitive to alkali, a coating upon the paper of a mixture of about one part of silicate of soda and nine parts of an equalizer, a coating of white clay mixed with sizing and a hardening agent', I

and a second coating of a mixture of about seven and a half parts of silicate of soda and two and a half parts of an equalizer.

FRANK A. MARTY.

REFERENCES CITED The following references are of record in the file oi this patent:

UNITED STATES PATENTS Number Name Date 2,043,860 Morgan June 9, 1936 2,062,179 Hunter v Nov. 24, 1936 2,327,380 Toland et al Aug. 24, 1943 2,361,665 Toland et al Oct. 3l, 1944 

